Magnetic states of a rf superconducting quantum interference device containing a double-barrier Josephson junction (original) (raw)
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Low-field magnetic response of multi-junction superconducting quantum interference devices
The European Physical Journal B, 2008
The magnetic states of multi-junction superconducting quantum interference device containing 2N identical conventional Josephson junctions are studied by means of a perturbation analysis of the non-linear first-order ordinary differential equations governing the dynamics of the Josephson junctions in these devices. In the zero-voltage state, persistent currents are calculated in terms of the externally applied magnetic flux Φex. The resulting d.c. susceptibility curves show that paramagnetic and diamagnetic states are present, depending on the value of Φex. The stability of these states is qualitatively studied by means of the effective potential notion for the system.
Macroscopic quantum behavior of superconducting quantum interference devices
Fortschritte der Physik, 2003
Superconducting quantum interference devices (SQUIDs) are made by a superconducting loop interrupted by one or more Josephson junctions. They are described in terms of a macroscopic variable, the magnetic flux, which shows quantum effects such as tunnelling through a potential barrier. Besides making up the source of a quantum state, SQUIDs also provide the instruments necessary for its probing: as a fact, SQUID based magnetometers have a sensitivity approaching the quantum limit. In this paper I will review the working principle of these devices and illustrate the system of SQUIDs realized in my group to test the quantum behavior at a macroscopic level. *
Superconducting Quantum Interference in Edge State Josephson Junctions
Physical Review Letters, 2020
We study superconducting quantum interference in a Josephson junction linked via edge states in two-dimensional (2D) insulators. We consider two scenarios in which the 2D insulator is either a topological or a trivial insulator supporting one-dimensional (1D) helical or nonhelical edge states, respectively. In equilibrium, we find that the qualitative dependence of critical supercurrent on the flux through the junction is insensitive to the helical nature of the mediating states and can, therefore, not be used to verify the topological features of the underlying insulator. However, upon applying a finite voltage bias smaller than the superconducting gap to a relatively long junction, the finite-frequency interference pattern in the non-equilibrium transport current is qualitatively different for helical edge states as compared to nonhelical ones.
Chapter 3 . Superconducting and Quantum-Effect Electronics
2009
Arrays of junctions provide for relatively large power but due to nonlinearities they can exhibit diverse complex spatiotemporal patterns. Experiments, simulations and analysis were performed on a broad range of discrete arrays of Josephson-junction oscillators in order to understand their ability to produce coherent radiation. Networks ranging from single square and triangular plaquettes to oneand twodimensional arrays are studied. In each array, the junctions are identical and underdamped, and the arrays are driven by dc bias currents. Although few analytical results are known for these systems, we study the technically interesting solutions which can be represented as traveling waves. It is in this mode that the devices can be used as submillimeter wave sources.
ISRN Condensed Matter Physics
The reduced dynamical model of a two-junction quantum interference device is generalized to the case of time-varying externally applied fluxes with a d. c. component and an oscillating addendum whose frequency is comparable with the inverse of the characteristic time for flux dynamics within the superconducting system. From the resulting effective single-junction model for null inductance of the superconducting loop, it can be seen that the critical current of the device shows a dependence on the frequency and amplitude of the oscillating part of the applied flux. It can therefore be argued that the latter quantities can be considered as control parameters in the voltage versus applied flux curves of superconducting quantum interference devices.
Physical Review B, 2010
We present a detailed analysis of the dependence of the critical current Ic on the magnetic field B of 0, π, and 0-π superconductor-insulator-ferromagnet-superconductor Josephson junctions. Ic(B) of the 0 and π junction closely follows a Fraunhofer pattern, indicating a homogeneous critical current density jc(x). The maximum of Ic(B) is slightly shifted along the field axis, pointing to a small remanent in-plane magnetization of the F-layer along the field axis. Ic(B) of the 0-π junction exhibits the characteristic central minimum. Ic however has a finite value here, due to an asymmetry of jc in the 0 and π part. In addition, this Ic(B) exhibits asymmetric maxima and bumped minima. To explain these features in detail, flux penetration being different in the 0 part and the π part needs to be taken into account. We discuss this asymmetry in relation to the magnetic properties of the F-layer and the fabrication technique used to produce the 0-π junctions.
Persistent currents in superconducting quantum interference devices
Physics Letters, Section A: General, Atomic and Solid State Physics, 2009
Starting from the reduced dynamical model of a two-junction quantum interference device, a quantum analog of the system has been exhibited, in order to extend the well known properties of this device to the quantum regime. By finding eigenvalues of the corresponding Hamiltonian operator, the persistent currents flowing in the ring have been obtained. The resulting quantum analog of the overdamped two-junction quantum interference device can be seen as a supercurrent qubit operating in the limit of negligible capacitance and finite inductance.
arXiv (Cornell University), 2024
Semiconductor-superconductor hybrid nanocircuits are of high interest due to their potential applications in quantum computing. Semiconductors with a strong spin-orbit coupling and large gfactor are particularly attractive since they are the basic building blocks of novel qubit architectures. However, for the engineering of these complex circuits, the building blocks must be characterized in detail. We have investigated a Josephson junction where the weak link is a two-dimensional electron gas (2DEG) hosted in an InAs/InGaAs heterostructure grown on a GaAs substrate. We employed the in-situ epitaxially grown Al layer as superconducting contacts to form an rf SQUID, and also to create a microwave resonator for sensing the Josephson inductance. We determined the gate-dependent current-phase relation, and observed supercurrent interference in out-of-plane magnetic fields. With the application of an in-plane magnetic field, we induced asymmetry in the interference pattern, which was found to be anisotropic in the device plane.